T105s-what's bulk vs absorbtion?

[jpendoley]

I have a bank of (4) T105s hooked up in parallel and series to provide 450A for my house bank. I have one Morningstar Tristar 30 MPPT controller regulating the charge from 240 Watts of solar (2 120W Kyoceras wired in parallel).
I am setting up a custum charge profile because the stock profiles on the Morningstar are not what the manufacturer calls for on the battery spec sheets. Trojans say they want 14.82V in "bulk" and 13.5 in float. Trojan does not specify an "absorption" stage, but Morningstar does not offer a "bulk" setting only an absorption.
Should I treat bulk and absorption as one pahse and charge at 14.82?

[cofc]

Yes, bulk and absorb are the same voltage. The batteries will never reach 14.8 while in bulk, because the charge will have switched to absorption by then.

[Adelie]

Originally Posted by jpendoley

I have a bank of (4) T105s hooked up in parallel and series to provide 450A for my house bank. I have one Morningstar Tristar 30 MPPT controller regulating the charge from 240 Watts of solar (2 120W Kyoceras wired in parallel).
I am setting up a custum charge profile because the stock profiles on the Morningstar are not what the manufacturer calls for on the battery spec sheets. Trojans say they want 14.82V in "bulk" and 13.5 in float. Trojan does not specify an "absorption" stage, but Morningstar does not offer a "bulk" setting only an absorption.
Should I treat bulk and absorption as one pahse and charge at 14.82?

There are 3 stages of battery charging:
Bulk
Absorption
Float

Bulk charging is when the battery will accept as many amps as your charger can supply. If you are starting at 50% this is load will be so hi it will drag the voltage down significantly. As the battery recharges is will start offering some resistance and the voltage will climb.
When the voltage reaches the limit you have set (14.8v) a good charger will start limiting the volts going in to that setting and the amps will start tapering off. This is the absorption phase.
At some point when the battery bank is "full" the charger will shift to the float voltage (13.5v) which will compensate for self discharge without boiling off water or outgassing hydrogen and oxygen that has been electrolyzed. As I understand it the shift to float is best done when the charging current reaches 0.005C, that is 0.5% of total bank capacity. The problem is that on cruisers a lot of charging is done while there are still house loads so the charger never sees current drop enough to trigger the switch to float. You could separate banks and only charge the unused bank. Generally chargers use a timer from when the battery become voltage limited.

[goboatingnow]

Bulk charging is a part of the charge curve of FLA where the maximum current is delimited by the batteries charge acceptance , it’s not a feature of your chargers ability per se. Many chargers activity enter a controlled constant current phase for bulk and then switch to CV for absorption

[jpendoley]

So let me regurgitate to see if I understand what you all are saying:

Bulk- the controller will give the battery as much current at as high a voltage as it will accept?

I asume there is a voltage limit beyond which my batteries can not accept current? For example my panels will put out 18-19 V but the controller steps it down to an acceptable limit. Morningstar lets me adjust that limit and I currently have it set at 15.0 V except for when I manually ask for an equalization.

Absorption- This stage is triggered when the battery reaches a voltage where it cannot accept ALL current at the bulk voltage level. In my case, because bulk and absorption Voltage is the same, (14.82) the controller will limit current to the level the battery can accept. So where the battery would accept 14 amps at 14.82 in bulk, it might only accept 7A in absorption at the same 14,82 V.

Float-The controller senses the battery has reached theoretical full charge and reduces voltage to the float charge (in my case 13.5V) and limits current to just enough to counter self discharge.

My controller lets me extend programmed absorption and float times if the battery leaves the absorption or float stages early. For example, controller and battery were in absortion stage for a couple of hours, but the battery dropped down to bulk due to a load (like the fridge) therefor in the next absorption stage the controller can be programmed to extend absorption for some increment of time longer.

Equalize: I think I get that. Essentially a higher than normal charge is applied (in my case 16,2V) to temporarily raise the voltage of the battery high enough to "boil" for a lack of a better term-the electrolyte to help slow down sulfation.

Anything wrong with my understanding of the process? The Morningstar software (morningview) allows a lot of custimization of charging profiles, but the explanantion of cause and affect is not that well documented. I don't want to undercharge or overcharge my battery bank. Considering whether I need another panel-I've got 240 W now (I'm on a mooring) and rarely get to float. Fridge is the only load during the week...

[wholybee]

Originally Posted by jpendoley

So let me regurgitate to see if I understand what you all are saying:

Bulk- the controller will give the battery as much current at as high a voltage as it will accept?

I asume there is a voltage limit beyond which my batteries can not accept current? For example my panels will put out 18-19 V but the controller steps it down to an acceptable limit. Morningstar lets me adjust that limit and I currently have it set at 15.0 V except for when I manually ask for an equalization.

Absorption- This stage is triggered when the battery reaches a voltage where it cannot accept ALL current at the bulk voltage level. In my case, because bulk and absorption Voltage is the same, (14.82) the controller will limit current to the level the battery can accept. So where the battery would accept 14 amps at 14.82 in bulk, it might only accept 7A in absorption at the same 14,82 V.

Float-The controller senses the battery has reached theoretical full charge and reduces voltage to the float charge (in my case 13.5V) and limits current to just enough to counter self discharge.

My controller lets me extend programmed absorption and float times if the battery leaves the absorption or float stages early. For example, controller and battery were in absortion stage for a couple of hours, but the battery dropped down to bulk due to a load (like the fridge) therefor in the next absorption stage the controller can be programmed to extend absorption for some increment of time longer.

Equalize: I think I get that. Essentially a higher than normal charge is applied (in my case 16,2V) to temporarily raise the voltage of the battery high enough to "boil" for a lack of a better term-the electrolyte to help slow down sulfation.

Anything wrong with my understanding of the process? The Morningstar software (morningview) allows a lot of custimization of charging profiles, but the explanantion of cause and affect is not that well documented. I don't want to undercharge or overcharge my battery bank. Considering whether I need another panel-I've got 240 W now (I'm on a mooring) and rarely get to float. Fridge is the only load during the week...

That is the general idea. While in bulk, the current will be the max the charger can supply to the battery, while the voltage will rise as the battery charges.

When the voltage reaches the Absorption voltage, the charger will hold that voltage and not let it rise any further. As the battery continues to charge, current will go down.

When current gets low enough that the charger thinks the battery is full, it switches to float.

[goboatingnow]

Originally Posted by wholybee

That is the general idea. While in bulk, the current will be the max the charger can supply to the battery, while the voltage will rise as the battery charges.

When the voltage reaches the Absorption voltage, the charger will hold that voltage and not let it rise any further. As the battery continues to charge, current will go down.

When current gets low enough that the charger thinks the battery is full, it switches to float.

Sheesh , again when in bulk , the maximum current will be delimited by the charge acceptance ability of the battery. That current might be in excess of your chargers ability or less then it , for example a high capacity charger and a low capacity battery can still be bulk charged

Remember loads set current not voltage sources.

Bulk , current will initially be the maximum of charger ability or battery acceptance limit. Voltage will rise and current will fall as this mode progresses

Absorption , the changeover point is somewhat arbitrary ,around 14.5 or slightly higher but below the gassing voltage but what happens is the charger limits the voltage rise ( ie CV operation) , current will flow according to the batteries characteristics , but will be reducing further

Absorption cutoff , again an arbitrary point , either tripped by a low current or time or both

Float mode , a maintainence voltage around 13.8v to overcome self discharge

[Moontide]

Prior posts are right and you don't need to be considered about charge rate of voltage in the absorption stage, provided you have your controller settings correct.



If you are not getting to float you might want to go ahead and add a panel to your current setup. FLA's like getting to float.



You can also set the max current the controller will send to the batteries. As I recall for FLA the charge max is 10% of AH capacity (double ck that). Since you have a 30 amp charger and 450 AH of batteries should not be an issue. But be aware if you go up in panels and controller it might become an issue.



Morningstar has a good white paper on their site about why it is fine to have more panel capacity than controller capacity. Many will argue that one should never do that but the paper makes a pretty compelling case on why it is OK, even cost effective and beneficial.

[Adelie]

Originally Posted by goboatingnow

Bulk charging is a part of the charge curve of FLA where the maximum current is delimited by the batteries charge acceptance , it’s not a feature of your chargers ability per se. Many chargers activity enter a controlled constant current phase for bulk and then switch to CV for absorption

Try again.

Internal resistance of a battery is related to state of charge, the lower the state of charge the lower the resistance.

With a battery discharged to 50% the internal resistance is pretty low and the battery can accept a lot of amps.

The voltage, amperage, resistance relationship is represented by the following formulae:

V = I × R
I = V / R
R = V / I

All the same but rearranged so you can pick the one you want for the variables you already have.

If you put a 5A charger on the battery it will give you 5A regardless of how many amps the battery could accept. So charge voltage sags until all 3 are in equilibrium.

If you put a 50A charger on it the voltage would sag less.

As the battery charges resistance rises, amps stays the same because that’s all the charger can provide and voltage rises.

When the voltage gets to whatever you have set it for the charger limits output to share voltage and amps starts to taper off.

FLAs and Gels don’t like to be bulk charged fast or they suffer damage, Gels especially. Bulk amps should be limited to 0.10-0.13C, that is 10-13% of bank size. For a 200Ahr bank you should be bulk charging at 26A max.

AGMs are the opposite. They don’t like to be bulk charged slow, 0.2C minimum, 0.3-0.4C better. That means for a large bank you should have a lot of charging capacity UNLESS you don’t regularly draw the bank down below about 75-80%.

[Dave Lochner]

There is a simpler way to understand this.

There are 3 stages to charging LA batteries,

Constant Current
Constant Voltage
Float

In the Constant Current stage, the charging source produces as much current as it can and as the battery can absorb. The voltage will start low and as the battery becomes more fully charged the voltage will rise until it reaches the "bulk voltage".

Once the bulk voltage is reached, the charging source holds the voltage steady and the current being sent to the battery reduces gradually because the battery's acceptance rate declines due to internal resistance. This is sometimes called the absorption stage.

When the battery can only accept an amp or so of current, the charging source changes to float with minimal current and voltage in the neighborhood of 13.4.

Each battery manufacturer has a different voltage for the switch from CC to CV and for float, follow their recommendations.

[goboatingnow]

Originally Posted by Adelie

Try again.

Internal resistance of a battery is related to state of charge, the lower the state of charge the lower the resistance.

With a battery discharged to 50% the internal resistance is pretty low and the battery can accept a lot of amps.

The voltage, amperage, resistance relationship is represented by the following formulae:

V = I × R
I = V / R
R = V / I

All the same but rearranged so you can pick the one you want for the variables you already have.

If you put a 5A charger on the battery it will give you 5A regardless of how many amps the battery could accept. So charge voltage sags until all 3 are in equilibrium.

If you put a 50A charger on it the voltage would sag less.

As the battery charges resistance rises, amps stays the same because that’s all the charger can provide and voltage rises.

When the voltage gets to whatever you have set it for the charger limits output to share voltage and amps starts to taper off.

FLAs and Gels don’t like to be bulk charged fast or they suffer damage, Gels especially. Bulk amps should be limited to 0.10-0.13C, that is 10-13% of bank size. For a 200Ahr bank you should be bulk charging at 26A max.

AGMs are the opposite. They don’t like to be bulk charged slow, 0.2C minimum, 0.3-0.4C better. That means for a large bank you should have a lot of charging capacity UNLESS you don’t regularly draw the bank down below about 75-80%.

Have a bash at reading the intro post https://www.cruisersforum.com/forums...ance-1442.html before you start making Ri claims

I merely pointed out that the charge acceptance rate may be above or below the chargers capability , bulk does not automatically assume the current is the chargers max ability. I countered the mistaken “ assumption “ that a charger will supply its max current during bulk , it may or it may not.

[jpendoley]

Thank you to everyone for great information. I've been calculating all of my loads and fine tuning my charging regimen in anticipation of going cruising. This has shown me that my current setup, in New England, is a little under sized in terms of panels. The stock charging profiles on my morningstar charger have charge rates that are significantly different from what Trojan wants to see. Fortunately, there is a custom charge profile that is user defined. All of your explanations are helping me sort it out. Thank you again-this forum is fantastic.
Jim

[Stu Jackson]

Originally Posted by jpendoley

Thank you to everyone for great information. I've been calculating all of my loads and fine tuning my charging regimen in anticipation of going cruising. This has shown me that my current setup, in New England, is a little under sized in terms of panels. The stock charging profiles on my morningstar charger have charge rates that are significantly different from what Trojan wants to see. Fortunately, there is a custom charge profile that is user defined. All of your explanations are helping me sort it out. Thank you again-this forum is fantastic.
Jim

Jim, I find it fascinating that in this day and age people are still retyping the basics of how batteries get charged. There are so very many avenues available to you as to how this works, including books and the internet.


You may learn a great deal from the information on Maine Sail's website. MS is a trusted name in boat electrical systems.



This particular article discusses the terms and the meaning of the terms for battery charging, from the "horse's mouth" so to speak. Factor the reality MS presents with some of the misinformation provided in some of the comments here, as well meaning as they may be.


https://marinehowto.com/how-fast-can...ry-be-charged/

[Flatswing]

Here's a simple explanation in diagrammatic form on page 2 from East Penn:
https://www.eastpennmanufacturing.co...eters-1913.pdf

[jpendoley]

Flatswing-thanks for that graphic-it was helpful. Stu-I've read Calder and Casey and some of Mainsails stuff-that link you shared was fantastic. I think some of the confusion is casued by the manufacturers themselves and the sometimes confusing marketing language they use. That, and some of us are just electrically challenged
All the advice is deeply appreciated.
Jim